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ext4: fix cgroup writeback accounting with fs-layer encryption 

When writing a page from an encrypted file that is using
filesystem-layer encryption (not inline encryption), ext4 encrypts the
pagecache page into a bounce page, then writes the bounce page.

It also passes the bounce page to wbc_account_cgroup_owner().  That's
incorrect, because the bounce page is a newly allocated temporary page
that doesn't have the memory cgroup of the original pagecache page.
This makes wbc_account_cgroup_owner() not account the I/O to the owner
of the pagecache page as it should.

Fix this by always passing the pagecache page to
wbc_account_cgroup_owner().

Fixes: 001e4a8775 ("ext4: implement cgroup writeback support")
Cc: stable@vger.kernel.org
Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230203005503.141557-1-ebiggers@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Eric Biggers 2023-02-02 16:55:03 -08:00 committed by Theodore Ts'o
parent e3645d72f8
commit ffec85d53d
1 changed files with 6 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
fs/ext4/page-io.c
View File

@ -409,7 +409,8 @@ static void io_submit_init_bio(struct ext4_io_submit *io,
static void io_submit_add_bh(struct ext4_io_submit *io, static void io_submit_add_bh(struct ext4_io_submit *io,
struct inode *inode, struct inode *inode,
struct page *page, struct page *pagecache_page,
struct page *bounce_page,
struct buffer_head *bh) struct buffer_head *bh)
{ {
int ret; int ret;
@ -421,10 +422,11 @@ submit_and_retry:
} }
if (io->io_bio == NULL) if (io->io_bio == NULL)
io_submit_init_bio(io, bh); io_submit_init_bio(io, bh);
ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh)); ret = bio_add_page(io->io_bio, bounce_page ?: pagecache_page,
bh->b_size, bh_offset(bh));
if (ret != bh->b_size) if (ret != bh->b_size)
goto submit_and_retry; goto submit_and_retry;
wbc_account_cgroup_owner(io->io_wbc, page, bh->b_size); wbc_account_cgroup_owner(io->io_wbc, pagecache_page, bh->b_size);
io->io_next_block++; io->io_next_block++;
} }
@ -561,8 +563,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
do { do {
if (!buffer_async_write(bh)) if (!buffer_async_write(bh))
continue; continue;
io_submit_add_bh(io, inode, io_submit_add_bh(io, inode, page, bounce_page, bh);
bounce_page ? bounce_page : page, bh);
} while ((bh = bh->b_this_page) != head); } while ((bh = bh->b_this_page) != head);
unlock: unlock:
unlock_page(page); unlock_page(page);